Current level radar devices work using a particular radar principle in each case. The commercially available devices use either the pulsed or the FMCE radar method.
U.S. Pat. No. 7,710,125 B2 discloses a pulsed radar method in which a reference channel is used. DE 198 13 604 A1 discloses an FMCW radar method.
Pulsed level radar devices generate transmission pulses, which are emitted towards the filling material surface using a transmission antenna. These pulses are subsequently reflected (at least in part) from the filling material surface and possibly also from the container base, a separating layer between different filling media, and/or container installations or interference points. The reflected transmission pulse is subsequently received by a receiving antenna (which may also be the transmission antenna) and converted into an intermediate-frequency pulse. This is followed by analogue/digital conversion and signal processing, which should ultimately deliver the desired measurement result.
Another level radar principle is the FMCW principle, which is based on frequency-modulated continuous waves. FMCW level radar devices do not transmit (discrete) transmission signal pulses, but rather continuous waves from the antenna towards the filling material surface, specifically using a frequency sweep or a frequency ramp. In this case too, the reflected signal is received by a corresponding receiving antenna and converted into an intermediate-frequency signal, which is subsequently fed to an analogue/digital converter and downstream signal processing.
The pulse and FMCW radar devices may be used in a wide range of applications. The hardware of these two families of radar devices is very different in construction, in particular as regards the construction of the high-frequency (HF) front end and the actuation thereof. The HF front end consists of those assemblies of the radar device which are directly involved in generating the transmission signal and generating the intermediate-frequency reception signal.